Gear cutter



GEAR CUTTER Qriginal Filed March 2, 1936 2 Sheets-Sheet l FIG.I5.- K

56 I INVENTOR ERNEST C-HEAD FIG.|4. so BY M W'Wlw 62 6| PM ATTORNEYS June24, 1947. QHEAD Re. 22,891

GEAR CUTTER Original Filed March 2, 1936 2 Sheets-Sheet 2 INVENTOR ERNEST C-HEAD (UM 4.2L: MW

3 M g ATTORNEYS- Reissued June 24, 1941 on'lii itit Ernest head; deceased, lateof Gleason Works, Rochester, N. Y.-, asslg'nee or g al No. 21,2": ;0'03, dated 3 Serial No; 66,672; March i for reissue September 14, 1945; serial N 62- 7 Claims. 1

The invention relates to face mill cutters for cutting spiralb'ev'el gears; pim'oris and the like, and ls more partidirl-arly concerned with face mill cutters designed for rough cutting the gears p'riorto' the finish butting operation. some of the features of'the invention are improvements on or ar related to the invention of the application of said Ernest Head; Serial No. 25,061, filed June v1935, now abandoned The invention'also' relates to an improved meth- 0d 015 rough: cutting spiral bevel ears by rheans or which the: cutting or the gears can be done more expeditiously and a greater amount of finish outting performed-with the finishing dutb efore it is necessary to sharp'en'the cutter blades thereof:

Tl'1'=pririeipal object of the invention is to prov'iae a face mn gear eutter whoseblades have a; definite and' arriple ar'noimtl or side or radial clearance regardless of the amount of top cleartim which' g'ear outter has provision for maintaining a fixed diameter andwidth of slot.

Another object of" the invention ,is" to provide a 'roii'ghing' outte'r' in which the blades, are so sharpened that the bottom of the slot'in the gear is out to a Width more closely approximating the desired width iii the finished gear than the side portions of the slot. One of the purposes of this construction is to'enable the tips of the blades in th finishing" cutter to do relatively less work than the sides of th'e'blades', thereby materially increasing the life of the finishing eutter blades.

airoughing cutter constrncted inthis manner it is" ai f je'atufef of" this invention that means are'providedfor mummy a'djiistingth'e' inside and outside blades in order that the predetermined diameter" and width of the bottom of the slot may be maintained when the blades are sharpeneuj back. p X The general objeetive's of the invention n 1entioned' above niay" be obtained by means of" various different const1 cti ons, and in the detailed description as hereinafterset-forth reference will e" e a t a lur ty, 9 t ,w t tions vd me ing considerablyin some respeots but having in coinn'ion certain novelinventive ieatures Reference shouldbe made to the'drawings, in which I) i ure 7 i .Pl n ewv.eo a a e. m cutter embodying the; inventionwith representative cutsbl d h nr ep asm: ,v a

b Figure? 15- a partiahsideview thereof in deq meni- Figure-Bis a seetionaiview oh tii lin 3 of emit 616,448 (cl. 5 165) Figure ,I; -,i-llustrat-in the relativfi a djustment 0f their-wide. and utside, cutting b a e lFieureA isgandiaerammatio iew i us r ing th'e superposedcutt-ing blades in relation to the 5 slot whiieh-th yare;d i ned o; u r

-Figiirei 5y-is; aMsim-ilar view showing blades a modified shape;.. a a m, Fi ure ,fif iswaeplan. view f a o fied Late mill cuttri employing separate slotting and side cutting blades; e Figurel is a' partial side view thereof in development.;... l e J 1'. a" e i. F ure 8r-is a "54 10 1?! vi w= nthe;. n ..r8:: .o Figure fi iI'Iust'ra-tingtherelative-,adjllfitmem betweeneslottin c andvsidetoutz insi blad ie l ,Figure 9; is a;fragmentary;s eotional viewshowingtheadiustmentnf anothersl insbla e; t Figure .10 isteadlag am a-ti xlli wt lus r t n the superposed Cutting blades adjusted to' form a==rodghihgouttery .e v v H i Figure 1=1; is anenlargedend; view; of the cutting pointp'fion'eanf wthe slotting b1ades; e Figure 12is-a-simi1ar view of a modified constructiomll. i Figur 13-'is a similar view 'ofa, further modifioation; .i 1 a. Figureliisza diagrammatic view showing successive positionsioflhe cutter'durin the generating motion whe'ncuttineamnion; e,

v Figure 415* is flitflPflViW ;o1'i theairiside blade; 15 illustrating; the method of obtaining the radial clearanbeuCL is l wFigurerlfiisga, similar-review of; the outside blade 16"shoWing*the--method' of obtaining the radial clearanoe nc'h e "A facesmilliciittihg to'olconstructed-in aceordante, WithLOhyfOIIii of the invention is illustratedin-Figuresxl' to .4: ,In this? cutter; theater'- mate blades are insid .q t eszblades l5'tand u ide swcu'ttinae lades .f fihlrflhi se' bla s ar 2a1tan ed n are an l r: ser esin th mi ahead and e tendin aedir tiom enera na a le eQ' 21 2 15 9 tth shfi q when; r swe side of th head, Figure 2; but ar A resp ti t e axi pit h ad. hen vie ed" in i ecr s es n :lF su e. fllie i side b ade a e n li e ihrespect tQ this than gl a, that; e insi w r ezw e a the ou s de... w ssflfige i ine :awn-angle-a sx hat t e b ade a ;p intinee wardl 9 t,fi ilnqlln qeil'l- $19 1 .13 .QI astli el d iem ie izo thet eadr and are s idah n h slots 92 Permit t e;das re t dju tm ie; Ant-e iest ns st l -enaes sa ki 'ed den erean paralleling the'inclination of the blade and'has an enlarged h'ead 8| engageable in a recess 82 in the shank of the blade. Each blade is secured in adjusted position by a bolt 83, the head of which bears against the outsid face of the shank. An elongated aperture 84 in the shank is of suflicient length to permit the desiredrange of adjustment. v

The inside cutting blade 15 has an inside cutting edge 85 and a top cutting edge 86 formed by the intersection of the front face 81 with the inside face 88 and top cutting face 89 respectively. Correspondingly the outside blade 16 has an outside cutting edge 98 and a top cutting edge 9I formed by the intersection of the front face 92 with the outside face 93 and the top face 94 respectively. The front faces 81 and 92 of the inside and outside blades are inclined at rake angles 81 and M respectively which are in opposite directions in the two blades. The inside face 88 f the inside blade 15 is relieved back of the cutting edge 85 to form side clearance, and the side clearance angle is indicated at c, Figure 1. The corresponding relief in the outside surface 93 of the outside blade 16 forms the side clearance angle 0'. The top face 89 of the inside blade has a top clearance angle indicated at d, Figure 2, while the top face 94 of the outside blade has a top clearance angle (1.

The position of the inside and outside blades in relation to the slot to be cut is shown diagrammatically in Figure 4 where it will be readily seen that the inside of the slot is formed by the inside blade 15 only, and the outside of the slot is formed by the outside blade 16 only. In one form of the present invention the cutting portions of the blades have the top end portions thereof shaped to produce an enlarged width of slot at the bottom thereof. Thus the inside blade has the straight line portion 95 for cutting the inside of the slot but has a portion 96 of different shape at the top of the blade which merges with the top cutting edge 86. As shown in Figure 4, the portion 96 has an inclination less than the inclination of portion 95 and is curved at its juncture with the top edge 86 to form a rounded corner where it joins top edge 86. The outside blade 16 also has a top edge 86, a'straight side cutting portion 91, and a shaped top portion 98 of lesser pressure angle which is curved at its juncture with top edge 86 to form a rounded corner where it joins said top edge. These shaped portions 96 and 98 may be termed slotting porticns of the blades since they produce an enlarged width at the bottom of the slot. The slotting portions of the blades may, if desired, extend at right angles to the edge 86 as illustrated in Figure 5 at the points 99 and I08, in which case there will be no side clearance component due to the top clearance. Also the portions 96 and 98 of the blades may be otherwise shaped to remove a larger amount of stock at the bottoms of the slots than would be obtained if the blades maintained the straight lines 95 and 91 to the top edges thereof.

Figure 15 illustrates the method of obtaining the radial clearance c on the inside blade 15. As mentioned above in connection with Figure 5, when the shaped portions 99 and I88 are at right angles to the top edge 86, there is no side clearance component due to the top clearance. This portion of such a blade would cut an annular slot having straight side walls. Also blades having the top portions 96 and 96, Figure 4, of slight angle would cut materially an annular slot. It will be seen that all points of this blade I cacti 4 back of the cutting edge must travel around the annular slot cut by the blade and have clearance so no rubbing action takes place between the blade and the work. Therefore, the blade must have a top clearance d and a side clearance from front to back 0 as shown by the line 18. The line 10 as will be seen from Figure 15 is struck from a center 1| offset back from the center 12 of the cutting tool so that as the front cutting edge travels in a true circular path indicated by the dotted line 13 the rear edge of the blade has side clearance with respect thereto. It will thus be seen that when the inside blade is sharpened back, it will cut the inner wall of the slot to a greater diameter.

Figure 16 is a corresponding view of the outside blade 16. This blade must have a top clearance d and a side clearance from front to back 0 as shown by the line 14. The line 14 is struck from a center 69 offset forwardly from the center 12 so that as the front cutting edge travels in a true circular path indicated by the dotted line 68, the rear edge of the blade has side clearance with respect thereto. It will thus be seen that when the outside blade is sharpened back, it will cut the outer wall of the slot to a smaller diameter.

The curved line 10 of the inside blade and the curved line 14 of the outside blade may be obtained in any suitable manner in order to properly provide the necessary radial clearance c and c. One method of grinding this relief is shown in the above mentioned application, Serial No. 25,061, filed June 3, 1935.

In accordance with the present invention, means is provided so that substantially a fixed diameter and width of slot will be obtained regardless of how far the blades are sharpened back. This is done by adjusting the inside blade in the direction of the angle a and the outside blade in the direction of the angle a. These angles are predetermined from the clearance angles of the cutting blades and may be determined by certain formulas. The formula for the inside blades is:

tangent c tangent a=tangent d The formula for the outside blades is:

tangent c From these formulas the values of the angles a and a may be determined and the slots in the cutter head 11 constructed to correspond with these angles.

One of the advantages of a cutter head constructed in this manner is that when the blades are sharpened back, they may be easily adjusted in the slots to obtain a fixed diameter and width of slot. Thus it is only necessary to adjust each of the blades so that the tips of the blades are at a fixed axial distance from the cutter head which may readily be obtained by a gauge block and the desired diameter and width of slot will au- 1 tomatically be obtained. Each time the blades are sharpened back they are adjusted in this manner to the fixed axial distance and the cutter is then ready for use.

With a face mill cutter as above described, the inside blade 15 cuts the bottom and inside of the slot, while the outside blade 16 cuts the bottom and outside of the slot. With respect to the finished dimensions of the slot, there is more stock removed at the bottom than at the sides so that in the finishing operation whether it be by means of a finishing face mill cutter or by means of a grinding wheel, less stock is required to be removed at the bottom of the slot than at the sides thereof. This effects a material saving in the life of the finishing apparatus since it is at the points of the cutting blades, or the grinding wheel, as the case may be, Where the most severe wear occurs.

A modified form of face mill cutter is illustrated in Figures 6 -to 9. In this form of the invention four diiierent kinds of blades are used for cutting different portions of the profile of the slot. Two of theseblades are termed slotting blades since they are used for cutting only in the bottom of the slot. The other two blades are termed side cutting blades" and one is adapted for cutting the inside profile of the slot and the other the outside. The'two slotting blades are also designed so that one cuts the inside bottom portion of the slot and the other the outside bottom portion. The blades maybe grouped together in different ways, but as illustrated the order is first a slotting blade, then a side cutting blade, then a slottingblade, etc. Thus as shown in Figures 6 and 7, I represents an inside side'cutting blade,

SO represents the outside slotting blade, is the outside side cutting blade and S1 is the inside slotting blade. All of the blades are held in the blade holders in the head by means of clamp-ing boltsv 83.

The side cutting blades may be positioned radially in any suitable manner such as by employing shims l4 and IS in the back of the slots forming the blade holders. The side cutting blades are also arranged to provide an axial adjustment and for this purpose the shank of, the blade is provided with a transverse groove 16 for receiving the projecting lip I! of the shim 14. This shim I4 is in turn provided with a recess I8 in which the head IQ of the adjusting screw 20 engages. The adjusting screw is threaded in an axially extending threaded hole 2| and is provided with a socket head 22 by which adjustment is made from the top of the cutter head.

The slotting blades are also adjustable in the head but preferably in such a manner as to adjust the same not only axially but also radially. Accordingly the slots 23 forming the blade holders are. arranged at an angle, the inside slotting blade SI pointing inwardly and the outside slotting blade 80 pointing outwardly. The adjusting screws for the slotting blades are threadedly adjusted in a direction parallel to, the respective slotting blades so that the head is of the adlusting, screw may directly engage the recess iii in the shank of the blade.

Figure shows the relative positions of the four types. of cutter blades during one type of cutting operation. The slotting blade S0 is ap d to cut. that portion of the slot from the point 24 to the point 25,. The inside slotting blade SI cuts the, portion of the slot from the point 26 to the point; 21.. The, inside blade I cuts the surface of the slot from the point 2.1 to the top of the. slot, whereas the outside blade 0 cuts the surface of the slot from the point 24' to the top of the same.

The primary advantage of the use of the two overlapping slotting blades for the outside and "-inside'slotting' respectively is that it enables the slot width to be maintained constant after the slotting blades become worn and require resharpening. To do this the slotting blades SI and SO are adjusted by their respective adjusting screws and because ofthe angle of these bladesiin the cutter head, the' inside slotting blade will be thereby movedzradiallyinward as well as axially, while'the outside slotting blade will be moved radially outward as well asaxially. To compensate for the axial movement of the slotting blades the side cutting blades 0. and I may be correspondingly adjusted in an axial direction.

Another advantage of the use of twoslotting blades is that it enables the most desirable shear and rake angles to be ground on both 'theoutside and inside slotting blades. Thus as illustrated, 28 represents the front rake angle of the outside slotting blade and 29 represents the side shear angle. The inside slotting blade S1 is made with a front rake angle 30 and a side shear angle 3|.

The inside and outside side cutting blades are similar to the conventional blades used in face mill cutters and can be made by the usualm'e'thods of construction. However, the clearance angles for the top clearance may be constructed to be of the theoretically correct angle for most efficient cutting whereas in the blades heretofore made the clearance angles have necessarily been a compromise due to the fact that in the conventional blade which cuts on the side 31 and the top 31a simultaneously, thetop clearance angle 32 must be great enough to give sufficient side clearance. In other words, the side clearance angle is a component of the'top clearance angle 32 and varies with the tangent of the pressure angle. Therefore, if angle 32 is made large enough to give the proper side, clearance, then angle 32 is too great'for eflicient top cutting and conversely, if angle 32 is made correct for top cutting, then side clearance is not sufficient for side cutting.

As the side cutting blades in the improved cutter do not cut on the top 31 it will be apparent that the clearance angle 32 in the blades is made suflicient to give the most eflicient side clearance. Also, side rake angle. 34 is made according to the best known practice. for a side cutting tool without requiring modification-because of any top out.

All points of each of the slotting bladesSO and SI back of the cutting edges must. travel around the annular slot cut by the blades. andhave clearance so that no rubbing action takes place be tween the blades and the work. Therefore each blade must have atop. clearance 38, slotting blade SO must have on the outside surface a side clearance 39 from front to back, and inside blade SI must have the side clearance 40 on the inside surface. The front rake angle ground on each of the slotting blades is difierent,,the outside slotting blade having the front rake angle 28 and the inside slotting blade having the rake angle 3.0. The side shea angles are different on the two slotting blades, the outside slotting blade having the side shear angle 25 andthe inside slotting blade having the side shear angle- 3|. It. should be observed that the top. clearance. angle 38 on each slotting blade is less. than the top clearance angle on the side cutting blades. The top clearance angle. 38. of the. slotting, blades. can be made in. accordance with the best practice suited for its. particular work and need not. be the same as the correspondin angle in. the side cutting blades.

The side-clearance angle; 10 on the. inside surface of the insideslotting blad'eis essential to the successful operation, of the cutter, and to better explain this. the cutting. Point of the slotting blade SI has been shown in large views in Figures 11 to 13 inclusive which illustrate several forms of the invention. In Figure 11, the small radius 42 at the corner of the cutting edge stops at a point 43. In this form of the slotting blade there will be a top clearance component at the point 43. Then it is necessary to have only a slight side clearance 40 from the point 43 at the front of the blade to the point 44 at the back of the blade.

Another modified form is shown in Figure 12 in which a portion48 of the cutting edge tangent to the radius 49 is made to angle outward to the point 50. Here again there is a side component to the top clearance angle but an additional clearance is necessary at 50 so that the blade will clear in the slot cut.

Figure 13 represents another modified form of blade similar to that disclosed in Figure 15 except that from the point 46 the side edge runs straight down and side clearance back of this edge is provided.

In each of the Figures 11, 12, and 13 Only the inside slotting blade SI has been shown, and it will be noted that the inside edge, which is at the left in these figures, is in contact with the slot while the other edge clears the slot. Consequently it is unnecessary to provide special clearance on the latter side of the inside slotting blade. The distance between the outside surface of the inside slotting blade and the walls of the slot is exaggerated in the drawings. The construction of the outside edge of the outside slotting blade SO complementary to the inside slotting blade SI has not been illustrated in Figures 11 to 13 but it will be understood that it will be constructed in accordance with the same principles as the blade SI.

Figure 14 illustrates the invention as applied to the rough cutting of a spiral bevel pinion whether by means of the two-blade type of cutter first described or the four-blade type of cutter subsequently described. The successive positions which the cutter will take in rolling out the curved shape of the tooth are shown. Spiral bevel pinions cut with this cutter are usually developed by the well known generating method in which the pinion is rolled with the cutter as said pinion would roll with a crown gear of the system. The cutter in this case represents the crown gear. By rolling the cutter and pinion together as shown in Figure 14, curves 55 and 56 are developed on the sides of the tooth space and fillet curves 59 and 60 are generated at the junctures of the tooth sides with the bottom of the tooth space. Curves 51 and 58 represent the shape of the sides while curves BI and 62 represent the shape of the fillet portions of the finished tooth space. These curves are such as would be generated by a conventional finishing cutter having cutting edges of one pressure angle for their full height, and they illustrate the amount of stock left for the finishing cutter to remove after the rough-generating operation.

It will be seen that each side of the roughed tooth space is really generated with a cutter having one pressure angle for the main portion of its height and having a protruding portion at its tip. The upper side cutting portions generate curves 55 and 56 of a given pressure angle and the rounded corners at the tips of the blades generate curves 59 and ill. The fact that the corners at the points of the roughing blades project laterally beyond the side-cutting edges of the blades means that different fillet curves 59, 60 are generated in the bottom of a tooth space by the roughing cutter than the fillet curves BI, 62 generated by the finishing cutter. The nature of the fillet curve generated in the roughing operation is such that more stock is removed than would be if the blade had the same pressure angle at the point as along the rest of its height. Therefore the corners of the cutting blades of the roughing cutter undercut a greater amount and leave a minimum amount of stock for the finishing cutter to remove between surfaces 59 and GI and also be tween surfaces El] and 62. The amount of stock left for finishing is greater between curves 55 and 51 and also between curves 56 and 58, and is uniform for these portions of the tooth space. While the generation of pinions in the manner illustrated in Figure 14 is usually employed for the rough cutting operation, it should be understood that a cutter designed to operate in the same manner may also be used for finish cutting if it is desirable to give extra relief or clearance at the bottom of the tooth.

In the preceding description of the various modifications of the invention, it has been shown that the invention may be embodied in cutters differing considerably in their specific constructions. In every case, however, there are certain underlying novel features, the chief of which is the provision of means for maintaining a fixed diameter and width of slot when the cutter blades are resharpened.

What is claimed as the invention is:

1. A face mill gear cutter, comprising a rotary head and a plurality of annularly arranged cutting blades which are secured thereto and extend in a direction generally parallel to the axisof the head when viewed from one side of the head, but which are inclined to the axis of the head when viewed in a cross-section through the axis of rotation of the head, each of said blades having a, side surface which has a top portion and a bottom portion, both of said portions having positive pressure angles, said top portion having a pressure angle less than that of said bottom portion, each blade being relieved on said side surface back of its front face to provide cutting clearance.

2. A face mill gear cutter comprising a rotary head and a plurality of annularly arranged cutting blades secured thereto which extend in the direction of the axis of rotation of said head when viewed from one side of the head, but which are inclined to the axis of the headin a cross-section through the head, the cutting part of each of said blades having a side surface which has a top portion and a. bottom portion, the bottom portion extending for the greater part of the height of the cutting part of the blade and having a straight profile of positive pressure angle, and the top portion being of different and lesser pressure angle than the pressure angle of the bottom portion.

3. A face mill gear cutter comprising a rotary head and a plurality of annularly arranged cutting blades, certain of the blades being outside blades and others of the blades being inside blades, the outside blades havin outside surfaces of two different pressure angles and the inside blades having inside surfaces of two different pressure angles, the outside surfaces, which are of smaller pressure angle, being relieved radially inwardly back of their front faces and the inside surfaces, which are of smaller pressure angle, being relieved radially outwardly back of their front faces, the blades which have the outside surfaces of smaller pressure angle being mounted in the cutter head to be inclined to and to extend outwardly from the cutter axis and to be adjustable I 9 in the direction of their inclination, and the blades, which have the inside surfaces of smaller pressure angle, being mounted in the cutter head to be inclined to and to extend inwardly toward the cutter axis and to be adjustable in the direction of their inclination.

4. A face mill gear cutter comprising a, rotary head and a plurality of annularly arranged cutting blades which have tip and side edges, certain of the blades being outside blades and others of the blades being inside blades, the outside blades having outside surfaces of two different pressure angles and the inside blades having inside surfaces of two different pressure angles, the outside surfaces, which are of smaller pressure angle, being relieved radially inwardly behind their side edges, the inside surfaces, which are of smaller pressure angle, being relieved radially outwardly behind their side edges, the blades, which have the outside surfaces of smaller pressure angle, being mounted in the cutter head to be inclined to and to extend outwardly from the axis of the cutter and to be adjustable in the direction of their inclination, and the blades, which have inside surfaces of smaller pressure angle, being mounted in the cutter head to be inclined to and to extend inwardly toward the axis of the cutter and to be adjustable in the direction of their inclination, the tips of the blades being relieved back of their tip edges to provide cutting clearance, the clearance angle on the tips of the blades being different from the clearance angles on the sides of the blades.

5. A face mill gear cutter comprising a rotary head and a plurality of annularly arranged cutting blades, certain of the blades being outside cutting blades and others of the blades being inside cutting blades, certain of the blades being outside slotting blades and others of the blades being inside slotting blades, the outside and inside cutting blades extending in the general direction of the axis of the cutter head and the outside and inside slotting blades being inclined outwardly and inwardly, respectively, with reference to the axis of the cutter head and being adjustable in the cutter head in the directions of their inclinations, the slotting blades having outside and inside surfaces of smaller pressure angle, respectively, than the corresponding side surfaces of the side-cutting blades, the outside slotting blades being relieved on their outside surfaces axially and radially inwardly back of their front faces, and the inside slotting blades being relieved on their inside surfaces axially and radially outwardly back of their front face.

6. A face mill cutter comprising a rotary head and a plurality of annularly arranged cutting blades, certain of the blades being outside blades and others of the blades inside blades, all of the blades being relieved on their tip surfaces back of their front faces, the outside blades having outside surfaces of two difierent pressure angles and being relieved on said side surfaces axially and radially inwardly back of their front faces, the inside blades having inside surfaces of two different pressure angles and being relieved on said side surfaces axially and radially outwardly back of their front faces, the outside blades being mounted in the cutter head to be inclined radially outwardly with reference to the axis of the cutter head, and the inside blades being mounted in the cutter head to be inclined radially inwardly with reference to the axis of the cutter head, the outside and inside blades being adjustable in the cutter head in the directions of their respective inclinations.

7. A face mill cutter comprising a rotary head and a plurality of annularly arranged cutting blades, certain of the blades being outside blades and others of the blades inside blades, all of the blades being relieved on their tip surfaces back of their front faces, the outside blades having outside surfaces of two different pressure angles and being relieved on said side surfaces axially and radially inwardly back of their front faces, the inside blades having inside surfaces of two different pressure angles and being relieved on said side surfaces axially and radially outwardly back of their front faces, the outside blades being mounted in the cutter head to be inclined radially outwardly with reference to the axis of the cutter head and the inside blades being mounted in the cutter head to be inclined radially inwardly with reference to the axis of the cutter head, the outside and inside blades being adjustable in the cutter head in the directions of their respective inclinations and the clearance angles on the side surfaces of the blades being different from clearance angle on the tips of the blades.

GLEASON WORKS, Assignee of Ernest C. Head, Deceased.

By JAMES E. GLEASON,

President.

REFERENCES CITED Name Date McMullen Sept. 18, 1945 Number 

